Updated October 18, 2026. Quick answer: Lines 1 to 4 are the Medical and Dental Expenses part of Schedule A. Line 1 is your total medical and dental expenses after reimbursements, line 2 is your adjusted gross income from Form 1040, line 3 is 7.5% of that income, and line 4 is what is left after subtracting line 3 from line 1. Only that remainder carries on toward your itemized total.
Related reading on this site: IRS Publication 554 and IRS Publication 502.
What lines 1 to 4 ask for
The form prints a warning at the top of the part: “Do not include expenses reimbursed or paid by others.” Then the four lines read “Medical and dental expenses (see instructions)”, “Enter amount from Form 1040 or 1040-SR, line 11b”, “Multiply line 2 by 7.5% (0.075)”, and “Subtract line 3 from line 1. If line 3 is more than line 1, enter-0-”. The instructions state the idea in one sentence: “deduct only the part of your medical and dental expenses that exceeds 7.5% of the amount of your adjusted gross income on Form 1040 or 1040-SR, line 11b.” The adjusted gross income line is explained on the Form 1040 lines 9, 10 and 11 page, and the choice between itemizing and the standard deduction is covered on the Form 1040 line 12 page.
Where the number on line 1 comes from
The instructions for line 1 say: “Enter the total of your medical and dental expenses after you reduce these expenses by any payments received from insurance or other sources.” On insurance paid directly to a provider they add: “include on line 1 only the amount you paid.”
For premiums, the instructions list “Insurance premiums for medical and dental care” among the payments you can include, and add “Reduce the insurance premiums by any” self-employed health insurance deduction claimed on Schedule 1. They also warn about premiums that were never taxed to you: “don’t include on line 1 insurance premiums paid by an employersponsored health insurance plan (cafeteria plan) unless the premiums are included in box 1 of your Form(s) W-2.”
The instructions go on to give long lists of examples of payments that can and cannot be included, and they point to “Pub. 502 discusses the types of expenses you can and can’t deduct.” Use those lists, not this page, to decide whether a particular bill counts.
Whose expenses count
The instructions say you can include bills you paid in 2025 for anyone who was one of the following either when the services were provided or when you paid for them: “All dependents you claim on your return.” The list also includes yourself and your spouse. If you paid for a parent’s care, the deducting a parent’s medical expenses page walks through that situation.
Where line 3 and line 4 come from
Line 2 is a copy of the adjusted gross income on Form 1040 line 11b, and line 3 is that amount times 7.5% (0.075). Here is a labelled illustration of the form’s own arithmetic, not an IRS example. Suppose line 2 were $60,000. Then line 3 would be calculated as $60,000 multiplied by 0.075, which is $4,500. Suppose line 1 were $7,000. Then line 4 would be calculated as $7,000 minus $4,500 and would come to $2,500. Suppose instead line 1 were $3,000. Then line 3 would be more than line 1, so the form says to enter -0- on line 4.
Where it goes next
Line 4 is one of the amounts added on the total line of the schedule. The form says “Add the amounts in the far right column for lines 4 through 16.” “Also, enter this amount on Form 1040 or 1040-SR, line 12e”. See Schedule A lines 17 and 18 for that step. The schedule is introduced on the Schedule A (Form 1040) page, and the return it attaches to is explained on the Form 1040 page.
Edition and line numbers
This page reads the 2025 Schedule A (Form 1040) and its 2025 instructions, the current files irs.gov served on 2026-10-18 (byte-identical to the archived copies). They are the files for the tax year 2025 return, filed in 2026. The schedule says “Attach to Form 1040 or 1040-SR.” Check the tax year printed on the schedule you are filling in and use the line numbers on that year’s schedule, because a different year’s schedule can number or word its lines differently.
Common mistakes
- Counting a bill that someone else paid or that insurance covered. The form warns “Do not include expenses reimbursed or paid by others.”
- Entering the full expense total as the deduction. The instructions say you “deduct only the part of your medical and dental expenses that exceeds 7.5% of the amount of your adjusted gross income”.
- Including premiums that came out of pay before tax. The instructions say “don’t include on line 1 insurance premiums paid by an employersponsored health insurance plan (cafeteria plan) unless the premiums are included in box 1 of your Form(s) W-2.”
Related: deducting a parent’s medical expenses, Form 1040 lines 9, 10 and 11, Form 1040 line 12, and Schedule A (Form 1040).
Sources
- Instructions for Schedule A (Form 1040), Itemized Deductions (2025): https://www.irs.gov/pub/irs-pdf/i1040sca.pdf
- Schedule A (Form 1040), Itemized Deductions (2025): https://www.irs.gov/pub/irs-pdf/f1040sa.pdf
Read from the IRS documents linked above on October 18, 2026. General information, not tax advice. Your own facts decide the outcome, and a preparer, the account provider or the IRS is the right place to confirm anything consequential.